1. Field of the Invention
The present invention relates to radar systems and, in particular, to a method and radar system for acquiring and tracking targets through the use of digital techniques performed primarily by a low cost, high reliability programmed digital computer.
2. State of the Prior Art
Typical prior art radar systems employ analog and digital techniques for performing the functions required to acquire and track targets in a radar system. For example, in previous radar systems, the target tracker and automatic gain control functions are typically hardware functions and the angular tracking error signals are usually developed by specific hardware elements. Such systems are typically very complex and, because of this complexity, are not as reliable as desired. Moreover, the versatility of such systems is minimal because changes in the hardware configuration require redesign and rewiring.
The use of a programmed computer to perform these functions is desirable but has presented numerous problems. In addition to the complexity of the functions performed in acquiring and tracking targets in a radar system and the resultant program complexity, typical hardware techniques cannot be directly employed. Moreover, it is desirable to employ a small, low cost, high reliability computer such as the Westinghouse Millicomputer but such computers have a memory structure which is very difficult to program for complex operations such as those encountered in a radar system.
Another major problem in employing a programmed computer is the timing associated with the transfer of information throughout the system. In a typical radar system employing a Millicomputer, multiple computers may be employed depending upon the basic instruction execution time of the selected Millicomputer. For example, a radar control computer may be utilized as a master computer and may request and send information from and to other computers by self-command. This intercomputer communication is via direct memory access (DMA). While one DMA is occurring, all others are prevented from occurring. Therefore, if the radar control computer is sending or receiving information from another computer and the digital signal processor (DSP) has information to send to the computer, the DSP must wait. If the DSP is made to wait too long, the information is lost. Therefore the timing for DMA's is critical.